Process for bending glass sheets



Patented Oct. 22, 1940 IUNITE-D I sTATEs PATENT OFFICE I PROCESS FDR GLASS. SHEETS v Grmond H. Paddockfltossford, Ohio, assignor to Libbey-Owens-Ford ,Glass Company, Toledo, Ohio, a. corporation of Ohio Application August 2s, 19's?, s'eriei Ne. 131,316

8 Claims. (01.49-84) me eide wens 1V and s adjacent the bottom s. The amesfrom the burners are directed up- The present invention relates to an improved process for bending glass sheets or plates and is of particular utility in the processing of relatively deep bends such as, for example, substantially U-shaped orV full semi-circular bends, al-

though the invention is'of course not restricted thereto. 1 n

Among the (objects of the invention is the provision of a process for bending glass sheets or plates .wherein the liability of breakage of the sheets or plates will be of an improved surface guality relatively free from distortion; wherein a minimum amount of burning and pitting of the f glass is obtained; and which is far superior, from 'a practical standpoint, to present da." methods of bending Other ob'jects and` advantages of the invention will become more apparent during the course of` Fig. 3 is a perspective sectional view of one 'of the sheet supporting rolls.

The process lprovided by the invention consists of a so-called over and under method of bending glass sheets or plates, being ofespecial utility in the'forming of relativelydeep bends.

- Brieiiy, the process includes two principal steps;

the first Hbeing the over-bend, wherein the glass sheet is bent over a suitable support or supports to effect a partial bend, and the second or finishtion of the partially bent sheet is reversed and supported in such reversed position, preferably ina. concave mold,.wherein the sheet is bent to the final predetermined curvat re.

in the practice of the initial bending step or overbend, the apparatus illustrated, in Eig. 1 of the drawing' maybe employed. 'Ihis apparatus coniremoved from beneath the sheetj whereupon ther.- I opposite end portions of the heated sheetwillo" prises a heating furnace 5 of. any suitable construction; the type offurnace illustrated being merely shown by. way of example. ,In'tlis case, however, the furnace comprises a bottom 6, opposite vertical side Walls 1 and' 8 and an arch.

The furnace may be'heated by the plurality of 455 gas burners I0 projecting through openings in."-

ing step being the under-bend inwhich the posi- .In carrying out the invention, 'and particularly glass is reduced to a minimum; wherein the bentwardly toward the arch 9 by vertical baille Walls Il and I2 disposed inwardlypf the side Walls 1 and 8 respectively, said baille walls 'terminating some distance beneathl the arch 9, so that the heating flames are directed upwardly and pass into the heating chamber, proper of the furnace adjacent the arch.. v g The heating chamber proper is designated I3v 10 and the initial step of bending the glass sheet I4 is adapted to take place therein. The glass sheet I4` is supported in a horizontal position, preferably upon a pair of .spaced parallel rolls I5 and I6, which rollsare disposed inwardly 01.15 the opposite ends of the sheet, with the distance4 between the rolls depending upon the radius and circumference or girth of bend desired. These rolls., which'vconstitute parallel lines of transverse support for the sheet, are mounted at each end upon a horizontal beam or the like I1 carriediat its opposite ends by posts or the like I8 and I9. .The supporting rolls I5 and I6 are adapted to be maintained in fixed position during the l nding operation and' this may be acg5 complishe by the chock or Wedge. blocks 20 vor in any other desired manner. l

While the sheet supporting rolls I5 and I6 may be of any-.desired construction, it is preferred that they be of asbestos orasbesto's covered so 30 as not to mar the surface of the glass. As shown in-.Fig. 3, each roll may consist of a cylindrical metallic body or core 2|, havingvv a covering 22' of asbestos.. n

After the supporting rolls I5 and I6 have been 35 properly spaced with relation to one .another an secured in position, the fiatsheet'of glass I4 to' be bent is laid thereon. In order to prevent the ,weight of the ends'of the sheet from breaking the glass, the said sheet may also be supported at its opposlteends upon4 rolls 23 and 24; said.

rolls being also mounted at their opposite'ends uponA the beams I'I and` being movable with respect thereto.

The glass sheet 'I4 is, then heated to the 4desired temperature and as the glass begins to soften and the supporting actionof the rolls 23 and 2.4 is-no longer necessary, the said rolls are be permitted to drop or bend downwardly by gravity, as indicated by the broken lines 25. Y In order tov limit the downward movement ofv the opposite end portions ofthe sheet, there are 4 providedfixa transverse stop members 2s and 21,

the position of these members depending'entirely upon the type` of bend desired. The stop members 26 and 21 vmay consist either of small guide rolls or of iron sections, such as straps or angles. Since the. outer edges of the glass sheet are usually trimmed off after'bending, iron sections may be used. However, it is preferred that asbestos covered rolls, such as shown in Fig. 3 be used, if the contacting lines would be visible in the completed bend.

The bending of the glass sheet over the rolls I5 and IB does not result in the sheet being bent to the iinal predetermined curvature, but results only in a partial or initial bend as explained above.

In making the finishing or under-bend, the

position of the partially bent sheet is reversed,

the sheet being supported in such reversed position and bent to the final predetermined curvature while so supported. Thus, the partially bent glass sheet 25 can be placed in a concave sand mold 28 (Fig. 2) or supported in some other desired manner. The mold 28 or other support can be arranged within the furnace 5 or in a Separate furnace which may be of the same construction as furnace 5 or of any other desired construction.

After the partially bent glass sheet ,has been placed in the mold 28, it is reheatedto cause a softening of the glass and this softening of the glass will 'cause it to drop and take the shape of the mold as indicated at 29, -the curvature of said mold corresponding to the final predetermined curvature desired of the sheet.

The mold 28y is preferably a customary sand It has been found, as a result of actual practice, that the process of over and under bending above described is far superior, from a practical standpoint, to present day methods of bending and results in a nished product of greatly improved surface quality and exceptional freedom from distortion. This is due in a large measure to the fact that there is no drag or slippage of the glass sheet over the supporting rolls I5 and l5, and likewise, there is relatively little slippage between the glass surface and mold surface which would tend to mar the glass. Consequently, sheets of large size can" be supported'and bent just as readily as small sheets. Also, in this process, each side of the glass is exposed approximately one-half the total bending time to those conditions4 which are considered of maximum severity. which results in a reduced amount of burning and pitting of the glass. As pointed out above,A this process is -of especial value in the making of any relatively deep bend, and is therefore not limited to the forming of substantially U-shaped or semi-circular bends.

It is to be understood that the form of the invention herewith shown and described is to be taken as the preferred embodiment of the same,

and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims. i

I claim:

1. The process of bending glass sheets, which i consists in supporting the sheet to be bent in a horizontal position upon spaced parallel lines of mold provided at its upper edges with the customary metal guide strips 30 and it is desired that when the glass sheet is originally placed in the mold the glass will not contact these metal strips. To avoid this, wooden strips or wedges (not shown) may be placed between the glass and metal strips 30 to compensate for'the differential in heat absorption between the glass and metal during the early stage of the heating cycle. These wooden strips or wedges gradually burn out, leaving the glass in Contact with the metal strips during the balance of the heating cycle. i

Any desired time and temperature cycle that will bend the glass can be used, the same cycle being preferably followed for both the over-bend and under-bend, with the exception that a -little more time and care may be given to finishing the sheet in the mold than in bending it over the after which the temperature is sharply increased f to from 1200 degrees F. to 1300 degrees 1T'. to effect the bending. yThe glass is allowed to'cool after which its position is reversed and it is placed in the mold28; where it is again heated,h

as above described, to effect the bending and nal shaping in the mold. To assist in ironing the'glass in the mold, a gas jetor wooden blocks may be used.

transverse support disposed inwardly of the 'ends of said sheet, heating the sheets to cause the outer ends thereof to bend downwardly over said lines of support to form a partial bend, reversing the position of the partially bent sheet and supporting itin such position, and in then heating the sheet to cause the bending thereof to the finished predetermined curvature while so supported. l

2. The process of bending glass sheets, which consists in supporting the sheet to be bent in a horizontal position inwardly of the ends of said sheet, heating the sheet to cause the outer ends thereof to drop downwardly by gravity to form a partial bend, reversing the position of the par-r tially bent sheet and vsupporting it in a concave mold, and in then heating the sheet to cause it to take the shape of said mold.

3. The process of bending glass sheets, which consists in suporting the sheet to be bent in a horizontal position upon spaced parallel lines of transverse support disposed inwardly ofthe ends of said sheet, heating the sheet to cause the outer i ends thereof to bend downwardly over said lines of support to form a partial bend, limiting the 4. The process of bendingglass sheets, which 4 consists in supporting the sheet to be bent in a horizontal position inwardly of the ends of said sheet, heating the ysheet to cause the outer ends thereof to drop downwardly by gravity to form a partial bend, limiting the downward movement of the ends of the sheet by mechanical means -engageable by said sheet, reversing the position of the partially bent sheet and supporting it in a concave mold, and in heating the sheet to cause it to take the shape of said mold.

5. The process of bending Aglass sheets, which consists 'in supporting the sheet to be bent in a horizontal position upon of said sheet, supporting the sheet at the opposite ends thereof, heating the sheet, withdrawing the support 'from the ds of the heated sheet causing said ends to bend downwardly by gravity over the lines of transverse support to form a partial bend, reversing the position of the partially bent sheet and suppring it in such'position, and'in 4 l then heating the sheet and causing it to take the iinal predetermined curvature while sp supported. 6. The process of bending glass sheets, which consists in supporting the sheet toV be bentin a horizontal position inwardly of the opposite ends thereof, also supporting theopposite ends of said sheet, heating the sheet, removing the support from' the opposite ends of the heated sheet thereby causing said ends to drop downwardly by gravityspaced parallel lines of `transverse support disposed inwardly of the ends horizontal position upon spaced parallel lines of transverse support disposed inwardly of the endsl of said sheet, supporting the sheet at the opposite ends thereof, heating the sheet, withdrawing the support from the ends of the heated sheet causing said ends to bend downwardly-by gravity over the lines of transverse support to form a partial bend,

limiting the downward movement of the ends of the sheet by mechanical means engageable by said ends, reversing the position of the partially bent sheet and supporting it in such position, and in then heating the sheetrand causing it to take the final predetermined curvature while so supported.

8. The process of bending glass sheets, which consists in supporting the sheet to be bent in a horizontal position inwardly of the opposite ends thereof, also supporting the ends of said sheet, heating the sheet, removing the support from the opposite ends of the heated sheet thereby causing said ends to drop downwardly by gravity to form a partial bend, limiting the downward 'movement of the ends of the sheet by mechanical means engageable by said ends, reversing the position of the partially bent sheet and supporting it in a concave mold, and in heating the sheet to cause it to take theshape of said mold. f

glass sheets, whichv ORMOND H. PADDOCK. 

